Extrusion press die assembly

ABSTRACT

Systems, devices, and methods for continuous extrusion of material billets are provided. A die assembly for press extrusion of a material includes a plurality of die plates forming a die body. The die body has an entrance and an exit having a diameter smaller than the entrance, with a tapered surface between the entrance and the exit. Each die plate has a center bore with a tapered interior surface, and the interior surfaces form the tapered surface that extends from the entrance to the exit. A base is coupled to the die body, and rotation of the base causes rotation of the die body. A billet pressed into the die body is heated by friction between the interior surface and an outer surface of the billet. The billet is heated to a deformable temperature and is extruded into a tube product as the billet is pressed from the entrance to the exit of the die body.

BACKGROUND

Tubing material, such as metal piping formed from copper, aluminum,metal alloy, or other metals, is often manufactured by extrusionprocesses. In an extrusion process, a large block of metal, referred toas a billet, is worked through a die structure having a circular orother configuration with an opening smaller than the size of the billetused to form the tubing material. The billet may be pre-heated to a hightemperature before a piercing rod is forced through the center of thebillet to form a channel therethrough. A large pressure, typically onthe order of 1,000 to 100,000 pounds-per-square-inch, is then applied tothe billet to force the pre-heated material over the piercing rod andthrough the die opening. The pressure forces the material to deform andextrude, exiting the back of the die as a tube having a diameter similarto the diameter of the opening of the die.

In order to produce large quantities of metal tubing by extrusion, largebillets and manufacturing machinery are required, and billets used inextrusion processes to create metal tubing often reach or exceed 1,000pounds in weight. The size of the machines and billets requires largemanufacturing facilities to produce the tubing, and the sizerequirements of the extrusion process lead to large start-up andmaintenance costs for the manufacturing operation. Furthermore,limitations of the processes, such as extruding only one billet at atime, lead to inefficiencies from billet sizes.

SUMMARY

Disclosed herein are systems, devices and methods for extrudingmaterials using a rotating extrusion press die assembly. In certainembodiments, the systems, devices and methods allow for continuousextrusion of a plurality of material billets. Such continuous extrusionallows for relatively smaller billets to be efficiently used to producea desired quantity of extruded material, and therefore the scale andsize requirements of such continuous extrusion press systems can besmaller than conventional extrusions processes.

In one aspect, a die assembly for extruding a material includes aplurality of die plates coupled together to form a die body. The diebody has a passage defining an entrance and an exit, and the diameter ofthe exit is smaller than the diameter of the entrance. A tapered surfaceis located between the entrance and the exit. Each of the die plates hasa center bore with a tapered interior surface around the center bore,and an interior surface of a center bore in a first die plate is taperedat a smaller angle relative to an axis of the passage than an interiorsurface of a center bore in a second die plate positioned adjacent to afront face of the first die plate. A base is coupled to the die body,and rotation of the base causes the die body to rotate.

In certain implementations, the second die plate is positioned nearer tothe entrance of the die body than the first die plate. The die assemblymay include a third die plate having a center bore with an interiorsurface that is tapered at a larger angle relative to the axis than aninterior surface of a center bore in a die plate positioned adjacent toa front face of the third die plate. The die plate positioned adjacentto the front face of the third die plate may be the first die plate, andthe third die plate may be positioned nearer to the exit of the die bodythan the first die plate.

In certain implementations, the die assembly includes a third plate thatforms a portion of the die body, and the third plate has a central borewith an interior surface around the center bore that is not tapered atan angle relative to the axis of the passage. The center bore of thethird plate defines the entrance of the die body. In certainimplementations, the base includes a center bore, and the center bore ofthe base has a diameter that is greater than a diameter of the die bodyexit.

In certain implementations, the die body is configured to receive abillet of material for extrusion, and the billet is not pre-heatedbefore entering the die body. Rotation of the die body creates frictionbetween the tapered interior surface and a billet advanced through theentrance and into the interior passage of the die body. The frictionheats the billet to a temperature that is sufficient to causedeformation of the billet material, and the heated billet is deformableunder a deformation force that does not exceed mechanical propertylimits of the billet material. Friction between the billet and a mandrelover which the billet is advanced heats the billet and the mandrel. Acooling system provides cooling fluid to an interior portion of themandrel.

In certain implementations, at least one of the die plates is formedfrom two different materials, with a first material forming a perimeterof a bore in the die plate and a second material forming an outerportion of the die plate. At least one of the first and second materialsis a ceramic material, a steel, or a consumable material. In certainimplementations, a front face of the die body near the entrance isconfigured to mate with a centering insert having a diametersubstantially equal to the diameter of the entrance. The centeringinsert and a perimeter of the entrance are formed from the samematerial.

In certain implementations, the die body is configured to receive amandrel tip through the entrance such that the mandrel tip ispositionable within the interior passage of the die body. The interiorsurface of the die body includes a complementary portion having an anglethat corresponds to an angle of an outer surface of the mandrel tip. Thedie body is configured to receive a billet pressed through the interiorpassage of the die body to form an extruded product, the extrudedproduct having an outer diameter corresponding to the diameter of theexit of the die body and an inner diameter corresponding to a diameterof the mandrel tip.

In one aspect, a die assembly includes a means for extruding a materialthat includes a plurality of plate means. The means for extruding has apassage means defining an entrance and an exit of the means forextruding, and the diameter of the exit is smaller than the diameter ofthe entrance. The means for extruding also has a tapered surface meansbetween the entrance and the exit. Each of the plate means has a centerbore with a tapered surface around the center bore, and an interiorsurface of a center bore in a first plate means is tapered at a smallerangle relative to an axis of the passage means than an interior surfaceof a center bore in a second plate means positioned adjacent to a frontface of the first plate means. The die assembly also includes a meansfor coupling the means for extruding to a rotation means, and rotationof the means for coupling causes the means for extruding to rotate.

In certain implementations, the second plate means is positioned nearerto the entrance of the means for extruding than the first plate means.The means for extruding may include a third plate means having a centerbore with an interior surface that is tapered at a larger angle relativeto the axis than an interior surface of a center bore in a plate meanspositioned adjacent to a front face of the third plate means. The platemeans positioned adjacent to the front face of the third plate means maybe the first plate means, and the third plate means may be positionednearer to the exit of the means for extruding than the first platemeans.

In certain implementations, the die assembly includes a third platemeans that forms a portion of the means for extruding, the third platemeans having a central bore with an interior surface around the centerbore that is not tapered at an angle relative to the axis. The centerbore of the third plate means defines the entrance of the means forextruding. In certain implementations, the means for coupling includes acenter bore. The center bore of the means for coupling has a diameterthat is greater than a diameter of the exit of the means for extruding.

In certain implementations, the means for extruding is configured toreceive a billet of material for extrusion, and the billet is notpre-heated before entering the means for extruding. Rotation of themeans for extruding creates friction between the tapered surface meansand a billet advanced through the entrance and into the passage means ofthe means for extruding. The friction heats the billet to a temperaturethat is sufficient to cause deformation of the billet material. Theheated billet is deformable under a deformation force that does notexceed mechanical property limits of the billet material. Frictionbetween the billet and a rod means over which the billet is advancedheats the billet and the rod means, and a means for cooling providescooling fluid to an interior portion of the rod means.

In certain implementations, at least one of the plate means is formedfrom two different materials, with a first material forming a perimeterof a bore in the plate means and a second material forming an outerportion of the plate means. At least one of the first and secondmaterials is a ceramic material, a steel, or a consumable material. Incertain implementations, a front face of the means for extruding nearthe entrance is configured to mate with a means for centering a billet,the means for centering having a diameter substantially equal to thediameter of the entrance. The means for centering and a perimeter of theentrance are formed from the same material.

In certain implementations, the means for extruding is configured toreceive a rod tip means through the entrance such that the rod tip meansis positionable within the interior passage of the means for extruding.The tapered surface means of the means for extruding comprises acomplementary portion having an angle that corresponds to an angle of anouter surface of the rod tip means. The means for extruding isconfigured to receive a billet pressed through the passage means of themeans for extruding to form an extruded product, the extruded producthaving an outer diameter corresponding to the diameter of the exit ofthe means for extruding and an inner diameter corresponding to adiameter of the rod tip means.

Variations and modifications of the embodiments discussed herein willoccur to those of skill in the art after reviewing this disclosure. Theforegoing features and aspects may be implemented in any combination andsub-combination, including multiple dependent combinations, andsub-combinations with one or more other features described herein. Thevarious features described or illustrated herein, including anycomponents thereof, may be combined or integrated in other systems.Moreover, certain features may be omitted or not implemented.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects and advantages will be apparent uponconsideration of the following detailed description, taken inconjunction with the accompanying drawings in which like-referencedcharacters refer to like parts throughout.

FIG. 1 shows a perspective view of an illustrative extrusion press dieassembly.

FIG. 2 shows a side elevation view of an illustrative extrusion presssystem.

FIG. 3 shows a side elevation view of the extrusion press die assemblyof FIG. 1.

FIG. 4 shows an illustrative steel end holder of the extrusion press dieassembly of FIG. 1.

FIG. 5 shows an illustrative entry plate of the extrusion press dieassembly of FIG. 1.

FIG. 6 shows an illustrative first intermediate plate of the extrusionpress die assembly of FIG. 1.

FIG. 7 shows an illustrative second intermediate plate of the extrusionpress die assembly of FIG. 1.

FIG. 8 shows an illustrative exit plate of the extrusion press dieassembly of FIG. 1.

FIG. 9 shows an illustrative base plate of the extrusion press dieassembly of FIG. 1.

FIG. 10 shows an illustrative cross-section view of the extrusion pressdie assembly of FIG. 1.

FIG. 11 shows an illustrative mandrel bar tip.

FIG. 12 shows an illustrative cross-section of the extrusion press dieassembly of FIG. 1 with the mandrel bar tip of FIG. 11 advanced into thedie assembly.

FIG. 13 shows a cross-sectional view of the die assembly and mandrel bartip of FIG. 12 during extrusion of a material.

DETAILED DESCRIPTION

To provide an overall understanding of the systems, methods, and devicesdescribed herein, certain illustrative embodiments will be described.Although the embodiments and features described herein are discussed foruse in connection with extrusion press systems, it will be understoodthat the components, connection mechanisms, manufacturing methods, andother features outlined below may be combined with one another in anysuitable manner and may be adapted and applied to systems to be used inother manufacturing processes. Furthermore, although the embodimentsdescribed herein relate to extruding metal tubing from hollow billets,it will be understood that the systems, devices, and methods describedherein may be adapted and applied to systems for extruding any suitabletype of material.

FIG. 1 shows a die assembly 1 for forming extruded tubing, which mayinclude seamless extruded tubing, in a press extrusion system. The dieassembly 1 may provide for continuous extrusion of a plurality ofbillets to produce a seamless extruded tubing product according tovarious seamless tubing standards including, for example, the ASTM-B88Standard Specification for Seamless Copper Water Tube. The seamlessextruded tubing may also comply with the standards under NSF/ANSI-61 forDrinking Water System Components. The die assembly 1 includes a mandrelbar 10 over which material billets, such as billet 17, are passed in thedirection of arrow A and through the die assembly to form an extrudedtubing product. The billet 17 may be formed from any suitable materialfor use in extrusion press systems including, but not limited to,various metals including copper and copper alloys, or any other suitablenon-ferrous metals such as aluminum, nickel, titanium, and alloysthereof, ferrous metals including steel and other iron alloys, polymerssuch as plastics, or any other suitable material or combinationsthereof. The billets passing over the mandrel bar 10 are advancedthrough a centering insert 9 and a die body 18, which is composed of astack of die plates 3-7 and a base plate 8, and through a cooling system13 to form the tube product. While die assembly 1 includes five platescoupled to a base plate, a die assembly may include more plates or fewerplates, and a die body may be longer or shorter than the die body 18 incertain applications.

During extrusion, the die body 18 rotates while billet 17 is pressedthrough the die body. The billet 17 is held by grippers 44 of thecentering insert 9, which does not rotate, and thus the billet 17 doesnot rotate as it enters the rotating die body 18 at the entrance 11 tothe center passage through the die body. The rotation of the die body 18creates friction with the outer surface of the non-rotating billet 17 asit is pressed through the die, and the friction heats the billet 17 to atemperature sufficient for the billet material to deform. For example, ametal billet may be heated by the friction to a temperature greater than1000° F. for deformation. The temperature requirements of differentmaterials and different metals may vary, and billet temperatures lessthan 1000° F. may be suitable in some applications. In contrast to otherextrusion systems, the die assembly 1 does not require pre-heating ofbillets before extrusion, as the rotation of the die body 18 and thefriction created by contact with the non-rotating billet 17 provideenergy that heats the billet to a deformable temperature.

The die assembly 1 may be used for forming an extruded material in anysuitable extrusion system, including, for example, the extrusion presssystem described in copending, commonly-assigned U.S. patent applicationSer. No. ______ (Attorney Docket No. 109965-0004-101), filedconcurrently herewith, and entitled “EXTRUSION PRESS SYSTEMS ANDMETHODS,” the disclosure of which is hereby incorporated by referenceherein in its entirety. For example, the die assembly 1 may beimplemented in the extrusion press system 57 shown in FIG. 2 forcontinuous material extrusion. The extrusion press system 57 includes amandrel carriage section 58 and a platen structure section 59. Themandrel carriage section 58 includes a mandrel bar 74, water clamps orcooling elements 60 and 61, mandrel grips or gripping elements 62 and63, and a billet delivery system. The mandrel carriage section 58 issupported by a physical carriage structure, which is not shown in FIG. 2to avoid overcomplicating the drawing, but which carriage structureserves as a mount for the components of the mandrel carriage 58. Theplaten structure section 59 includes an entry platen 65 and a rear dieplaten 66, press-ram platens 67 and 68, a centering platen 69, and arotating die 70 that presses against the rear die platen 66. The platenstructure section 59 is supported by a frame 71 that also serves as amount for the motor 72 and related gearbox components (not shown). Thedirection along which billet loading, transport, and extrusion occursaccording to the extrusion press system 57 is denoted by arrow B. Theextrusion press system 57 may be operated, at least in part, by a PLCsystem that controls aspects of the billet delivery subsystem 77,extrusion subsystem 78, and a cooling subsystem of the extrusion presssystem 57

The mandrel grips 62, 63 comprise a mandrel bar gripping system 73designed to hold the mandrel bar in place while allowing a plurality ofbillets to be continuously fed along and about the mandrel bar 74 toprovide for continuous extrusion. The mandrel grips 62, 63 may becontrolled by the PLC system to securely hold in place and prevent themandrel bar 74 from rotating such that at any given time during theextrusion process, at least one of the mandrel grips 62, 63 is grippingthe mandrel bar 74. The mandrel grips 62, 63 set the position of themandrel bar 74 and prevent the mandrel bar 74 from rotating. When themandrel grips 62, 63 are in a gripping position, thereby gripping themandrel bar 74, the mandrel grips 62, 63 prevent billets from beingtransported along the mandrel bar 74 through the grips.

The mandrel grips 62, 63 operate by alternately gripping the mandrel bar74 to allow one or more billets to pass through a respective mandrelgrip at a given time. For example, the upstream mandrel grip 62 mayrelease the mandrel bar 74 while the downstream mandrel grip 63 isgripping the mandrel bar 74. At any given time, at least one of themandrel grips 62, 63 is preferably gripping or otherwise engaged withthe mandrel bar 74. One or more billets queued or indexed near theupstream mandrel grip 62, or being transported along the mandrel bar 74,may pass through the open upstream mandrel grip 62. After a specifiednumber of billets have passed through the open upstream mandrel grip 62,the mandrel gripper 62 may close and thereby return to gripping themandrel bar 74, and the billets may be advanced to the downstreamgripping element 63. The downstream gripping element 63 may remainclosed, thereby gripping the mandrel bar 74, or the downstream mandrelgrip 63 may open after the upstream mandrel grip 62 re-grips the mandrelbar 74. Although two mandrel grips 62, 63 are shown in the extrusionpress system 57, it will be understood that any suitable number ofmandrel grips may be provided.

The water clamps 60, 61 comprise a mandrel bar water delivery system 75designed to supply cooling water along the interior of the mandrel bar74 to the mandrel bar tip during the extrusion process. The water clamps60, 61 may be controlled by the PLC system to continuously supplyprocess cooling water to the mandrel bar during the extrusion processwhile allowing a plurality of billets to be continuously feed along andabout the mandrel bar 74. The water clamps 60, 61 operate such thatthere is no or substantially no interruption to the supply of processcooling water to the mandrel bar tip during the extrusion process.Similar to the operation of the mandrel grips 62, 63 discussed above,when the water clamps 60, 61 are clamped to or engaged with the mandrelbar 74, the water clamps 60, 61 prevent billets from being transportedalong the mandrel bar 74 through the water clamps.

The water clamps 60, 61 operate such that at any given time during theextrusion at least one of the water clamps is clamped to or engaged withthe mandrel bar 74 and thereby delivers cooling water into the mandrelbar 74 for delivery to the tip of the mandrel bar. When a billet passesthrough one of the water clamps 60, 61, the respective water clampdiscontinues delivering cooling water and releases or disengages themandrel bar 74 to allow the billet to pass therethrough beforere-clamping the mandrel bar 74 and continuing to deliver cooling water.While one of the water clamps 60, 61 is unclamped or disengaged from themandrel bar 74, the other water clamp continues to deliver cooling waterto the mandrel bar.

For example, the upstream water clamp 60 may release the mandrel bar 74while the downstream water clamp 61 is clamped to the mandrel bar 74. Atany given time, at least one of the water clamps 60, 61 is preferablyclamped to the mandrel bar 74 to continuously deliver cooling water. Oneor more billets queued or indexed near the upstream water clamp 60, orbeing transported along the mandrel bar 74, may pass through the openupstream water clamp 60. After a specified number of billets has passedthrough the open upstream water clamp 60, the water clamp 60 may closeand thereby return to clamping the mandrel bar 74 and delivering coolingwater, and the billets may be advanced to the downstream water clamp 61.The downstream water clamp 61 may remain closed, thereby clamping themandrel bar 74, or the downstream water clamp 61 may open after theupstream water clamp 60 re-clamps to the mandrel bar 74. Although twowater clamps 60, 61 are shown in the extrusion press system 57, it willbe understood that any suitable number of water clamps may be provided.

The mandrel bar 74 extends along substantially the length of theextrusion press system 57 and is positioned to place the mandrel bar tipthrough the rotating die 70. The rotating die 70 may incorporate the diebody 18 shown in FIG. 1. The adjustment to properly position the mandrelbar tip through the die 70 is accomplished by moving the mandrelcarriage section 58, thus moving the mandrel bar 74. The adjustments tothe mandrel bar 74 and the mandrel carriage section 58 may be towards oraway from the die 70. The mandrel bar 74 and the mandrel carriagesection 58 preferably cannot be adjusted while the extrusion presssystem 57 is in operation, although it will be understood that incertain embodiments the mandrel bar 74 and/or mandrel carriage section58 may be adjusted during operation.

As discussed above, the extrusion press system 57 includes a platenstructure section 59 having an entry platen 65 and a rear die platen 66,press-ram platens 67 and 68, a centering platen 69, and a rotating die70 presses against the rear die platen 66. Near the entry platen 65 isthe press-ram platen assembly 76 that includes a first press-ram platen67, or A-Ram, and a second press-ram platen 68, or B-Ram. The first andsecond press-ram platens 67, 68 feed billets into the centering platen69, which grips the billets and prevents the billets from rotating priorto entering the rotating die 70, which presses against the rear dieplaten 66.

The press-ram platens 67, 68 operate by gripping the billets andproviding a substantially constant pushing force in the direction of theextrusion die stack 70. At any given time at least one of the press-ramplatens 67, 68 grips a billet and advances the billet along the mandrelbar 74 to provide the constant pushing force. The press-ram platens 67,68 form the final part of the billet delivery subsystem 77 before thebillet enters the centering insert 69 and the rotating die 70 of theextrusion subsystem 78. Similar to the billet feed track section beforethe entry platen 65, the section prior to the press-ram platens 67, 68preferably continuously indexes the billets to minimize any gaps betweena billet that is gripped by the press-ram platens 67, 68 and the nextbillet.

As discussed above, the press-rams 67, 68 continuously push billets intothe rotating die 70. The press-rams 67, 68 alternate gripping andadvancing billets towards and into the rotating die 70 and thenungripping the advanced billets and retracting for the nextgripping/advancing cycle. There is preferably an overlap between thetime when one press-ram stops pushing and the other press-ram is aboutto start pushing so that there is always uniform pressure on therotating die 70. The press-rams 67, 68 advance and retract via press-ramcylinders coupled to the respective press-ram. As shown there are twopress-ram cylinders 79, 80 per press-ram. A first set of press-ramcylinders 80 is located on the left and right of the entry platen 65(although the right-side press-ram cylinder is hidden from view behindthe left-side press-ram cylinder). The first set of press-ram cylinders80 couples with the first press-ram platen 67 and is configured to movethe first press-ram 67 as the first press-ram 67 advances billets andretracts to grab a following billet. A second set of press-ram cylinders79 is located to the top and bottom of the entry platen 65. The secondset of press-ram cylinders 79 couples with the second press-ram platen68 and is configured to move the second press-ram 68 as the secondpress-ram 68 advances billets and retracts to grab a following billet.Although two press-ram cylinders are shown for each of the first andsecond press-ram platens 67, 68, it will be understood that any suitablenumber of press-ram cylinders may be provided, and in certainembodiments press-ram cylinders may be coupled to both the first andsecond press-rams 67, 68.

The centering platen 69 receives billets advanced by the press-rams 67,68 and functions to hold the billets during the extrusion process priorto entry of the billets into the rotating die 70. When the centeringplaten 69 is positioned in place for the extrusion process, thecentering platen 69 substantially becomes part of the extrusion die 70.That is, a centering insert of the centering platen 69 substantiallyabuts the rotating die 70. The centering platen 69 itself, however, andthe components therein including the centering insert, do not rotatewith the rotating die 70. The centering platen 69 prevents the billetsthat are no longer held by the second press-ram from rotating while thedie 70 rotates by gripping the billets and thereby preventing thebillets from rotating prior to entry of the billets into the rotatingdie 70.

Referring back to the die assembly 1 of FIG. 1, when the assembly isused in an extrusion process, for example in the extrusion system ofFIG. 2, the centering insert 9 is advanced to the front edge of the diebody 18, such that a front surface 55 of the centering insert 9 contactsa front surface 16 of the die body 18. This orientation of the die body18 and the centering insert 9 during extrusion is shown in FIG. 3. Inthis orientation, the contact between the faces 55 and 16 of thecentering insert 9 and die body 18, respectively, prevents material fromescaping the die body 18 during the extrusion process. To begin theextrusion, a billet 17 is advanced over the mandrel bar 10 in thedirection of arrow A and through the die assembly 1 to press the billet17 into an extruded tube product. Before entering the die assembly 1,the billet 17 is advanced into the opening 15 of the centering insert 9,where grippers 44 engage the outer surface of the billet 17. As thebillet 17 is advanced through the opening 15, these grippers 44 preventrotation of the billet 17 when the billet 17 is contacted by therotating interior surface 14 of the die body 18.

While the billet 17 and centering insert 9 do not rotate during theextrusion process, the die body 18 and base plate 8 to which the diebody is connected are rotated by the motor-driven spindle 56. As thebillet 17 is advanced through the centering insert 9, it passes throughthe entrance 11 of the die body 18 and contacts the interior surface 14of the die body 18. A torsional force is applied to the outer surface ofthe billet 17 due to the interference contact between the rotating die18 and the billet 17. The grippers 44 of the centering insert 9 resistthis torsional force and prevent the billet 17 from rotating before itenters the die body 18, creating friction and producing the energy thatheats the billet 17.

The profile of the tapered interior surface 14 of the die body 18 isdefined by the shape and orientation of central bores that pass throughthe plates in the die body 18. The die body 18 is formed of a stack ofdie plates, including a steel end holder 3, an entry plate 4, a firstintermediate plate 5, a second intermediate plate 6, and an exit plate7. This series of plates that makes up the die body 18 are stackedtogether, secured to one another by a fastener, such as the bolt 2 inFIG. 1, and connected to the base plate 8. The bolt 2 is placed intoeach of the through-holes 12, which pass through each of the plates 3-8.The base plate 8 is then coupled to motor-driven spindle 56, whichrotates the plate 8, as well as the plates 3-7 of the die body 18. Incertain implementations, a die body may be employed that includes moreor fewer than the five plates 3-7 shown in die body 18.

The interior surface 14 created by the central bores of the plates ofthe die body 18 exhibits a tapered profile that narrows the interiorpassage through the die body 18 from the entrance 11 to an exit of thepassage at the exit plate 7. Thus, when force is applied to the billet17 to press the billet through the die body 18, the material of thebillet 17 is extruded as the outer diameter of the material is forced todecrease to pass through each of the plates 3-7. The dimensions of theplates 3-7, and the interaction between the interior surface 14 and thebillet 17, is described in more detail below with respect to FIGS. 4-13.

FIGS. 4-9 show each of the plates 3-7 in the die body 18, and the baseplate 8 to which the die body 18 is connected. FIG. 4 shows the steelend holder 3 of the die body 18 that forms the front face 16 of the diebody and the entrance 11 to the interior passage of the die body. Thesteel end holder 3 includes a central circular bore 21 that defines thediameter of the opening entrance 11 when stacked in the die body 18. Asshown in FIG. 4, the steel end holder 3 is formed from two materials,with the outer perimeter 19 of the plate formed from one material andthe perimeter 20 of the bore 21 formed from a different material. Thetwo materials that make up the steel end holder 3 may be chosen to formcomplementary interfaces between the steel end holder 3 and both thecentering insert 9 and the entry plate 4. For example, the outerperimeter 19 may be formed of a steel, such as H13 steel, that is thesame as or similar to the material that forms an outer perimeter of theentry plate 4, while the bore perimeter 20 may be formed of a differentmaterial, such as an inconel steel, that is the same as or similar tothe material used to form the centering insert 9. By matching thematerial of the bore perimeter 20 and the centering insert 9, the frontface 23 of the bore perimeter 20 that contacts the front face 55 of thecentering insert 9 provides a complementary interface that reduces wearwhen the die assembly 1 is in use. Because the die body 18 rotates andthe centering insert 9 remains stationary, friction may be createdbetween the face 23 and the face 55. By forming the bore perimeter 20and the centering insert 9 from the same material or similar materials,along with adjusting the pressure of surface 55 against surface 16, thewearing effect of this friction can be minimized, particularly duringstart up and shut down of the extrusion process when rotation of the diebody 18 starts or stops.

The second plate in the die body 18 is the entry plate 4, shown in FIG.5. As with the steel end holder 3, the entry plate 4 is formed from twodifferent materials. One material forms the outer perimeter 25 of theplate while a second material forms the bore perimeter 24 around thecentral bore 26 through the center of the plate. The outer perimeter 25may be made of the same material or a similar material as the outerperimeter of the steel end holder 3, for example H13 steel material. Theperimeter 24 of the bore 26 is formed from a wear-resistant material,for example a ceramic material, that resists degradation when a billet,such as billet 17, is pressed through the bore 26 and contacts theinterior surface 27.

The entry plate 4 begins the taper of the interior surface 14 of the diebody 18 from the entrance 11 to the exit of the die body. The interiorsurface 27 of the perimeter 24 is angled such that the diameter acrossthe diameter of the center bore 26 is greater at the front face of theplate 4 that abuts the back face of the steel end holder 3 and smallerat the back face of the entry plate 4 that abuts the first intermediateplate 5. When billet 17, having a diameter that is equal to the diameterof the bore 26 at the front face, is pressed through the entry plate 4,the tapering of the surface 27 creates friction between the rotatingplate 4 and the billet 17. This friction generates energy that heats thebillet 17 as it is advanced into the rotating die body 18, beginning thedeformation of the billet through the tapered interior surface 14. Incontrast to extrusion processes in which contact between a pre-heatedbillet and a non-rotating die creates heat energy as a by-product, thefriction heating of the non-pre-heated billet 17 is necessary forextrusion as it is needed to heat the billet to a temperature adequatefor deformation.

FIG. 6 shows the first intermediate plate 5 that is located behind theentry plate 4 in the stack of plates that make up the die body 18. Thefirst intermediate plate 5 includes an outer perimeter 29, formed from afirst material, and a bore perimeter 28, formed from a second material.The outer perimeter 29 may be formed of the same materials or similarmaterials as the outer perimeters of the other plates in the stack, forexample an H13 steel. Perimeter 28 of the center bore 30 through theplate is formed from a wear-resistant material, for example a ceramicmaterial, as discussed with respect to bore perimeter 24 of the entryplate 4. The inner surface 31 of the bore perimeter 28 is tapered fromthe front face of the first intermediate plate 5 that abuts the entryplate 4 in the stack to the back face of the first intermediate plate 5that abuts the second intermediate plate 6 in the plate stack. Theangling of the inner surface 31 tapers the center bore 30 from the frontface to the rear face and further tapers the interior passage andsurface 14 of the die body 18, as discussed above with respect to thecenter bore 26 of the entry plate 4.

The degree at which the inner surface 31 tapers with respect to a centeraxis of the central bore 30 in the first intermediate plate 5 relativeto the taper angle of the inner surface 27 of the entry plate 4 isdependent on the material being extruded and the total overall number ofdie plates. In certain implementations for a particular material, thedegree at which the inner surface 31 tapers may be less than the taperangle of the inner surface 27 of the entry plate 4. This change in theangle of the inner surface and the smaller diameter of the center bore30 relative to the center bore 26 may spread the frictional interfacewith the billet 17 and the work required to deform the billet 17 moreevenly over the entry plate 4 and the first intermediate plate 5,reducing material wear and extending the lifetime of the die plates aswell as improving concentricity and uniformity of an extruded product.This spreading of work and frictional force and the correlation betweenmaterials and the degree of surface tapering is discussed more fullybelow with respect to the cross sections shown in FIGS. 10, 12 and 13.

The second intermediate plate 6, which follows the first intermediateplate 5 in the die stack, is shown in FIG. 7. Similar to plates 3-5, thesecond intermediate plate 6 has an outer perimeter 32, formed of a firstmaterial, and a perimeter 33 around a center bore 34, formed of thesecond material. The first material that forms outer perimeter 32 may bethe same as or similar to the other plates in the stack, for example anH13 steel, and the material that forms the bore perimeter 33 may be awear-resistant material, such as a ceramic. The interior surface 35 ofthe perimeter 33 around the central bore 34 is angled from a front faceof the plate 6 that abuts the first intermediate plate 5 to a back faceof the plate 6 that abuts the exit plate 7.

The final plate in the plate stack that makes up the die body 18 is theexit plate 7, which is shown in FIG. 8. The exit plate 7, similar toplates 3-6, has an outer perimeter 36 formed from a first material, suchas an H13 steel, and a perimeter 37 around a central bore 38 formed froma second material, for example a wear-resistant ceramic. The diameter ofexit plate 7 is substantially smaller than the diameter of the opening11 at the steel end holder 3 shown in FIG. 4 as a result of the taperingof the interior surface 14 from the steel end holder 3 to the exit plate7. The interior surface 39 that surrounds the central bore 38 of exitplate 7 is angled with respect to a central axis of the center bore 38.The narrowest section of the center bore 38 defines the narrowestportion of the passage through the die body 18, and thus sets the outerdiameter of an extruded tube that is produced when a billet 17 ispressed through the die body 18. This diameter and the dimensions of theextruded product created using the die assembly 1 are discussed in moredetail below with respect to FIG. 13.

FIG. 9 shows the base plate 8, which couples the stacked plates thatform the die body 18 to a rotational power source. For example, as shownin FIGS. 1 and 3, the base plate 8 in the die assembly 1 couples the diebody 18 to a spindle 56. The spindle 56 is driven to rotate by a motorthat powers the rotation of the spindle 56 at a set rotational speed.The spindle 56 is connected to the base plate 8 by bolts which passthrough outer through-holes 43 around the perimeter of the base plate 8and transfer the rotational force of the spindle 56 to the base plate 8.

The base plate 8 is also rotationally coupled to the plates in the diebody 18 by bolts, such as bolt 2 shown in FIG. 1, that pass through thethrough-holes 12 of the die body 18 and into the holes 42 in the baseplate 8.

The base plate 8 includes a central bore 40 having an interior surface41. The bore 40 and the interior surface 41 define an opening in thebase plate 8 that may have a wider diameter than the diameter of thebore in the exit plate 7. The wider diameter of the base plate bore 40allows the extruded material to exit the die body 18 without directlycontacting the interior surface 41 and may allow for a coolingcomponent, such as a fluid source, to partially enter the base plate 8and apply a cooling fluid to extruded material exiting the exit plate 7near the exit of the die body 18. The exit plate 7 may also include arelief angle near the back face of the plate that further facilitatesthe application of cooling fluid, as discussed below with respect toFIG. 13.

The die assembly 1 is assembled prior to extrusion by stacking plates3-7 and connecting the die body 18 formed by the plates to the baseplate 8 with bolts placed into the through-holes 12 of the die bodyplates and into the holes 42 of the base plate. The stacking of theseplates to form the die body 18 forms the interior profile of the diebody 18 that causes extrusion of billets pressed through the dieassembly 1. This inner profile and the orientation of the stacked platesare shown in the cross-sectional view of the die assembly 1 in FIG. 10.

The cross section in FIG. 10 shows the die body 18 and the centeringinsert 9 positioned for extrusion. The die plates 3-7 are coupledtogether and fastened to the base plate 8 by bolts 2 inserted into theseries of through-holes 12 in the outer perimeters 19, 25, 29, 32, and36 of the plates. In this orientation, the opening 11 of the interiorpassage 54 in the die body 18 is aligned with the centering insert 9 toreceive a billet pressed through the opening 15 of the centering insert9 and into the die body 18 along the center axis 45 of the interiorpassage 54.

Each of the bore perimeters 23, 24, 28, 33, and 37 of the die plates 3-7abuts bore perimeters in adjacent plates to form the tapered interiorsurface 14 that outlines the interior passage 54 through the die body18. The inner surface 14 narrows the interior passage 54 from thelargest diameter of the passage at the opening 11 to the smallestdiameter at the exit 81, and the narrowing of the passage 54 causes thenarrowing deformation and extrusion of a billet pressed into therotating die body 18 during operation. The extrusion requires frictionenergy to be produced at the interface of the inner surface 14 to heatthe billet, and the energy can create wear on the bore perimeters of thedie plates 3-7. To reduce the effect of the friction wear and produceuniform stresses across the interior surface 14 during extrusion, theinner surfaces 27, 31, 35, and 39 are designed to spread the frictioninterface and reduce the concentration of energy and friction on any oneplate. The design of the inner surfaces and the profile of the interiorsurface 14 may differ for different applications, and in particular forthe extrusion of different materials. Depending on the materialproperties of billets used for extrusion, for example heat transferproperties that may affect the heating of the billets during extrusion,the inner profile of die plates in a die body may be varied to spreadwork and wear over the die plates. In addition, the die rotation speedmay be varied to increase the efficiency of the die and avoid exceedingmaterial properties of the billets. For example, a die rotation speedbetween about 200 rpm and about 1000 rpm may be used. In certainimplementations, a slower rotation speed, for example about 300 rpm, maybe desired to avoid applying a high level of torsional sheer to a billetwhile still heating the billet to a sufficient temperature fordeformation. A faster speed, for example about 800 rpm, may be used fora material that is not adversely affected by a higher torsional sheer orthat requires more energy, and thus greater friction, to heat to adeformation temperature. In other implementations, die rotation speedsin excess of 100 rpm may be desired for extrusion.

As shown in FIG. 10, the inner surfaces 27, 31, 35, and 39 do not taperat uniform angles with respect to the central axis 45. Each surface inthe depicted die is tapered at an angle that decreases from the entryplate 4 near the opening 11 to exit plate 7 at the exit 81. Thisdecreasing angle design may be desired for a particular extrusionmaterial or application of the die assembly 1. In certain embodiments,however, the taper angle of the interior surface 27 with respect to thecentral axis 45 may be equal to or less than the taper angle of theadjacent surface 31. In the embodiment shown in FIG. 10, the angle 46 atwhich the interior surface 27 of the entry plate 4 is tapered is greaterthan the angle 47 at which the interior surface 39 of the exit plate 7is tapered. The differences in taper angles between the plates spreadsthe frictional energy and stress over the plates as a result of thedifferences in diameters of the center bores from the opening 11 to theexit 81.

Each plate has an entrance diameter, for example diameter d5 of plate 4,and an exit diameter, for example diameter d7 of plate 4. When a billetis pressed into the plate, a threshold amount of energy must begenerated to heat and deform the billet from the diameter d5 to thediameter d7. This amount of energy is affected by the percent reductionin diameter, in particular the resulting percent reduction incross-sectional area of a billet as it passes through the plate 4. Ifthe central bores in plates 3-7 were each tapered at a single uniformangle, the diameter change from the entrance to the exit of each platewould be equal, and thus the percent reduction in billet cross-sectionalarea would increase for each successive plate. For example, if theabsolute difference between diameters d5 and d7 of plate 4 were equal tothe absolute difference between diameters d6 and d8 of plate 7, thepercent reduction in the diameter of the central bore would be higher inplate 7 than plate 4, and a greater amount of stress and energy couldcause plate 7 to wear faster than plate 4.

In addition to the percent area reduction of a billet over a plate,mechanical and thermal properties of the billet materials may dictatethe number and design of plates in a die stack. For example, a billetmaterial having high thermal conductivity may heat up to a deformabletemperature more quickly than a material having a low thermalconductivity, and thus a shorter die with fewer plates may be used forthe high conductivity material. In addition, the tapering angles of theinner surface of a die may be greater for the high conductivity materialas a result of the quicker heating of the billet. In otherimplementations, dies of equal size having the same number of plates maybe used, and the tapering angles of the dies may differ to accommodatethe different thermal properties and heat the billets to a deformabletemperature while spreading work and wear as evenly as possible over thedie surface and the surface of a mandrel tip within the die.

A billet pressed through the die body 18 produces an extruded tubeproduct through exit 81 of the die body 18 having an outer diameter thatis similar to the diameter d8, the diameter at the narrowest portion ofexit plate 7. The inner diameter of the extruded product is selected byadvancing the mandrel bar 10 into the die body 18 with a mandrel tiphaving an end dimension, selected to create the inner diameter of thetube product, at the end of the mandrel bar 10. FIG. 11 shows a mandreltip 48 that may be coupled to the end of the mandrel bar 10 to create adesired inner diameter for extruded tubing. The mandrel tip 48 has anopen end 82 that is configured to couple to the end of the mandrel bar10. The friction energy and heat generated during extrusion may heat themandrel tip 48, and the open end 82 may receive cooling fluid, such aswater or gas, from a cooling system that runs through the mandrel bar 10to cool the mandrel tip 48.

Opposite the open end 82 of the mandrel tip 48 is a closed end 51. Thediameter of the closed end 51 is the dimension that sets the innerdiameter of a tube extruded over the tip 48, and the tip 48 can beselected from a series of tips having different diameters to achieveextrusions with different inner diameter dimensions. Between the openend 82 and the closed end 51 are three portions 49, 83, and 50 of thetip outer surface 84. During extrusion, a billet is pressed over themandrel bar 10 and the tip 48 in the direction of arrow C such that thebillet passes over a deformation region including tip portions 49 and83, and an end portion 50. When the tip 48 is positioned for extrusion,the tip is advanced into a die until the closed end 51 extends beyondthe rear exit of the die at which the die diameter is narrowest. Abillet having a hollow core diameter substantially equal to the outerdiameter of the tip portion 49 is then passed over the mandrel bar 10and the tip 48. At the tip portion 49, the diameter of the surroundingdie narrows, and friction between the die and the billet creates energythat heats the billet as the outer diameter of the billet is compressed.The heated billet then passes over the tip portion 83, and the innerdiameter of the hollow core of the billet decreases to the outerdiameter of end portion 50 as the material extrudes. This extrusion overthe mandrel tip 48 is discussed in more detail below with respect toFIGS. 12 and 13.

FIG. 12 shows the die assembly 1 with the mandrel 10 and mandrel tip 48advanced through the centering insert 9 and into the center passage 54of the die body 18. The mandrel 10 is positioned such that the mandreltip 48 extends through the exit 81 in the exit plate 7. As discussedabove with respect to FIG. 2, gripping elements in an extrusion presssystem may be used to hold the mandrel bar 10 and in the orientationshown in FIG. 12 and to resist rotation while the die body 18 is rotatedand a billet passes over the mandrel bar 10.

FIG. 13 shows the die assembly and mandrel tip configuration of FIG. 12as the billet 17 is passed through the die body 18 and extruded to formtubing 53. During extrusion, the die body 18 is rotated while themandrel bar 10 and centering insert 9 are held stationary. The billet 17is pressed into the die body 18 in the direction of arrow A and contactsthe interior surface 14 of the die body 18 at a first contact point 85.The interference contact between the interior surface 14 and the billet17 begins at the contact point 85 and generates the energy that heatsthe billet 17 to a plastic deformable temperature.

As the billet 17 is advanced over the first portion 49 of the mandreltip 48, the taper of the interior surface 14 applies a compression forceto the outer surface of the billet 17 that presses the billet 17 inwardstowards the mandrel tip 48. Because the billet 17 is in a plasticdeformation state, the material in the billet extrudes in the directionof portion 83 of mandrel tip 48 as the die body 18 decreases the outerdiameter of the billet 17 from the original diameter d2. When the billet17 reaches the tip portion 83, the taper of the tip portion 83 towardsthe end portion 50 causes the inner diameter of the billet 17 to extrudeand decrease from the original diameter d1 as the billet advancesfurther over the mandrel tip 48. The tapered surface of the mandrel tip48 at the tip portion 83 may substantially correspond to the angle ofthe interior surface 14 in the area surrounding the tip portion 83 tocreate substantially uniform extrusion in that portion. For example, theouter and inner diameters of the billet 17 may decrease by substantiallythe same amount or by substantially the same percentage from the end oftip portion 83 proximate first tip portion 49 to the end of tip portion83 proximate end portion 50.

When the extruding billet 17 reaches the end portion 50, the innerdiameter of the billet is reduced from the original diameter d1 to thefinal diameter d3 of the end tubing product. As the billet 17 passesover the end portion 50, the outer diameter of the billet 17 continuesto decrease to the final outer diameter d4 when the extruded tubingproduct 53 exits the exit plate 7. At the point of exit, the formationof the extruded product 53 is complete. Due to the friction and heatingwithin the die body 18, the product 53 is at a heightened temperatureupon exit from the die body 18, and a cooling element may be applied toprevent further deformation or increase operational safety of theextrusion press, eliminate the escape of extruded material, or maintaindesired material characteristics. The bore 40 in the base plate 8 isshown in FIG. 13 with a diameter larger than the exit diameter of theexit plate 7. This configuration may be preferable in order to allowcooling elements and cooling fluid to reach into the base plate 8 andcontact the extruded product 53 as soon as it exits the final bearing inthe exit plate 7 for earlier cooling. The exit plate 7 includes anangled relief surface 86 to further facilitate the introduction of afluid material as near as possible to the exit 81 of the die body 18.After the product 53 exits the base plate 8 and passing through acooling system, the extrusion process is complete, and the product 53may be gathered for post-processing.

It is to be understood that the foregoing description is merelyillustrative and is not to be limited to the details given here in.While several embodiments have been provided in the present disclosure,it should be understood that the disclosed systems, devices and methodsand their components may be embodied in many other specific formswithout departing from the scope of this disclosure.

Various modifications will occur to those with skill in the art afterreviewing this disclosure. The disclosed features may be implemented inany combination and sub-combinations, including multiple-dependentcombinations and sub-combinations with one or more features describedherein. The various features described or illustrated above, includingany components thereof, may be combined or integrated into othersystems, Moreover, certain features may be omitted or not implemented.Examples of changes, substitutions and alterations are ascertainable byone skilled in the art and can be made without departing from the scopeof the information disclosed herein. All references cited herein areincorporated by reference in their entirety and made part of thisapplication.

1. A die assembly for extruding a material, comprising: a plurality ofdie plates coupled together to form a die body having: a passagedefining an entrance and an exit, wherein the diameter of the exit issmaller than the diameter of the entrance; and a tapered interiorsurface between the entrance and the exit; wherein each of the dieplates has a center bore with an interior surface around the centerbore, an interior surface of a center bore in a first die plate beingtapered at a smaller angle relative to an axis of the passage than aninterior surface of a center bore in a second die plate positionedadjacent to a front face of the first die plate; and a base coupled tothe die body, wherein rotation of the base causes the die body torotate.
 2. The die assembly of claim 1, wherein the second die plate ispositioned nearer to the entrance of the die body than the first dieplate.
 3. The die assembly of claim 1, further comprising a third dieplate having a center bore with an interior surface that is tapered at alarger angle relative to the axis than an interior surface of a centerbore in a die plate positioned adjacent to a front face of the third dieplate.
 4. The die assembly of claim 3, wherein the die plate positionedadjacent to the front face of the third die plate is the first dieplate.
 5. The die assembly of claim 3, wherein the third die plate ispositioned nearer to the exit of the die body than the first die plate.6. The die assembly of claim 1, further comprising a third plate thatforms a portion of the die body, the first plate having a central borewith an interior surface around the center bore that is not tapered atan angle relative to the axis.
 7. The die assembly of claim 6, whereinthe center bore of the third plate defines the entrance of the die body.8. The die assembly of claim 1, wherein the base comprises a centerbore.
 9. The die assembly of claim 8, wherein the center bore of thebase has a diameter that is greater than a diameter of the die bodyexit.
 10. The die assembly of claim 1, wherein the die body isconfigured to receive a billet of material for extrusion, and the billetis not pre-heated before entering the die body.
 11. The die assembly ofclaim 10, wherein rotation of the die body creates friction between thetapered interior surface and a billet advanced through the entrance andinto the interior passage of the die body.
 12. The die assembly of claim11, wherein the friction heats the billet to a temperature that issufficient to cause deformation of the billet material.
 13. The dieassembly of claim 12, wherein the heated billet is deformable under adeformation force that does not exceed mechanical property limits of thebillet material.
 14. The die assembly of claim 13, wherein frictionbetween the billet and a mandrel over which the billet is advanced heatsthe billet and the mandrel.
 15. The die assembly of claim 14, wherein acooling system provides cooling fluid to an interior portion of themandrel.
 16. The die assembly of claim 1, wherein at least one of thedie plates is formed from two different materials, with a first materialforming a perimeter of a bore in the die plate and a second materialforming an outer portion of the die plate.
 17. The die assembly of claim16, wherein at least one of the first and second materials is a ceramicmaterial, a steel, or a consumable material.
 18. The die assembly ofclaim 1, wherein a front face of the die body near the entrance isconfigured to mate with a centering insert having a diametersubstantially equal to the diameter of the entrance.
 19. The dieassembly of claim 18, wherein the centering insert and a perimeter ofthe entrance are formed from the same material.
 20. The die assembly ofclaim 1, wherein the die body is configured to receive a mandrel tipthrough the entrance such that the mandrel tip is positionable withinthe interior passage of the die body.
 21. The die assembly of claim 20,wherein the interior surface of the die body comprises a complementaryportion having an angle that corresponds to an angle of an outer surfaceof the mandrel tip.
 22. The die assembly of claim 20, wherein the diebody is configured to receive a billet pressed through the interiorpassage of the die body to form an extruded product, the extrudedproduct having an outer diameter corresponding to the diameter of theexit of the die body and an inner diameter corresponding to a diameterof the mandrel tip. 23-44. (canceled)